Inflammatory colorectal polyps (ICRPs) are commonly seen in miniature dachshund (MD) dogs; typically, multiple polyps form with severe neutrophil infiltration. ICRP is thought to be a novel form of inflammatory bowel disease (IBD), but its etiology has not been investigated. The innate immune system is implicated in the pathogenesis of both human and canine IBD. Therefore, the aim of the current study was to evaluate the messenger RNA (mRNA) expression profiles of pattern recognition receptors (PRRs) and cytokines in ICRPs. Polyp tissues were collected by colonoscopic biopsies from 24 MDs with ICRPs. Non-polypoid colonic mucosa was collected from all MDs with ICRPs and 21 clinically healthy beagles (as the controls). The expression levels of the mRNAs encoding toll-like receptors (TLRs) 1-10; nucleotide-binding oligomerization domain (NOD)-like receptors NOD1 and NOD2; and cytokines IL-1β, IL-6, IL-8/CXCL8, and TNF-α were evaluated by quantitative real-time RT-PCR. Three of the 10 well-known candidate reference genes were selected as housekeeper genes based on analyses from the GeNorm, NormFinder, and BestKeeper programs. Levels of TLR1, TLR2, TLR4, TLR6, TLR7, TLR8, TLR9, TLR10, NOD2, and all cytokines were significantly upregulated in the polyps relative to those in the controls. There was significant decrease in the expression levels of TLR3 and NOD1 in the polyp tissues compared to the non-polypoid colonic mucosa obtained from MDs with ICRPs. All upregulated PRR mRNAs were positively correlated with all proinflammatory cytokine mRNAs. This study demonstrated the dysregulation of PRRs and proinflammatory cytokines in ICRPs of MDs, which may play an important role in the pathogenesis of this disease.
Keywords: Inflammatory colorectal polyp; Innate immunity; Miniature dachshund; Pattern recognition receptor; Proinflammatory cytokine.
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